A total of 17 countries are currently deemed by the Foreign Office to be entirely unsafe for tourists. Here they are, in alphabetical order...

Afghanistan

Why? "Terrorists are very likely to try to carry out attacks in Afghanistan. Specific methods of attack are evolving and increasing in sophistication. Hotels and guesthouses used by foreign nationals and the government of Afghanistan are subject to regular threats. Travel by road throughout the country, but particularly outside the capital Kabul, is extremely dangerous."